How to compute the double integral over dx and dy?

7 次查看（过去 30 天）
Kalasagarreddi Kottakota
评论： Star Strider 2023-4-3
Hi, Can someone help me to how to code this equation in matlab? Let x and y are axis of a plane. dx and dy are increments. I have values of a and b at each coordinate(x,y) as shown in the below code.
clear all; close all;clc;
% Let
dx = 0.1;
x = -0.5:dx:0.5;
dy = 0.1;
y = -0.5:dx:0.5;
N = length(x);
a = randn(N,N);
b = randn(N,N);

请先登录，再回答此问题。

采纳的回答

Star Strider
Star Strider 2023-4-3
Ran in:
You are integrating matrices, so use trapz (or cumtrapz, depending on the result you want) once in each dimension —
% clear all; close all;clc;
% Let
dx = 0.1;
x = -0.5:dx:0.5;
dy = 0.1;
y = -0.5:dx:0.5;
N = length(x);
a = randn(N,N);
b = randn(N,N);
columnInt = trapz((a-b).^2) % Column Integrals
columnInt = 1×11
19.6448 26.9404 10.3535 10.6369 19.7843 13.8794 7.4786 12.1139 10.1436 22.0933 19.0884
rowInt = trapz(columnInt) % Integrate Column Integrals
rowInt = 152.7905
totalInt = trapz((trapz((a-b).^2))) % Both In One Line
totalInt = 152.7905
.
  2 个评论
Star Strider
Star Strider 2023-4-3
Ran in:
I initially forgot that. Assuming ‘x’ defines the columns and ‘y’ defines the rows —
% clear all; close all;clc;
% Let
dx = 0.1;
x = -0.5:dx:0.5;
dy = 0.1;
y = -0.5:dx:0.5;
N = length(x);
a = randn(N,N);
b = randn(N,N);
columnInt = trapz(x,(a-b).^2) % Column Integrals
columnInt = 1×11
3.2512 1.1639 1.0265 1.5750 2.4845 1.1630 3.4526 2.8748 1.7902 0.9262 3.7454
rowInt = trapz(y,columnInt) % Integrate Column Integrals
rowInt = 1.9955
totalInt = trapz(y,trapz(x,(a-b).^2)) % Both In One Line
totalInt = 1.9955
.

请先登录，再进行评论。

更多回答（2 个）

Samyuktha
Samyuktha 2023-4-3
Hi Kalasagarreddi,
I understand that you want to compute a double integral.
You can do this with the help of 'integral2' command. Please refer to the following documentation link for information on the syntax of 'integral2'.
integral2
Hope this helps!
Torsten
Torsten 2023-4-3
Ran in:
dx = 0.1;
x = -0.5:dx:0.5;
dy = 0.1;
y = -0.5:dx:0.5;
N = length(x);
a = randn(N,N);
b = randn(N,N);
F = (a-b).^2;
% Use one of the following approximations for the integral
I1 = trapz(y,trapz(x,F,2))
I1 = 2.0996
I2 = trapz(x,trapz(y,F,1))
I2 = 2.0996

类别

在 Help Center 和 File Exchange 中查找有关 Numerical Integration and Differentiation 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by